The invention relates to annular composite workpieces, in particular rolling bearing rings, and a cold rolling method for the manufacturing thereof from at least two hollow cylindrical workpieces made of different materials or the same materials with different strength (in the following different materials).
Occasionally the production of this kind of rolling bearing rings is described in the literature.
According to DE 200 923, an unhardened reinforcement ring is placed over a hardened ring after it has been finish—machined and filled with balls. It is pointed out that the bearing can accept more balls because the hardened ring deforms elastically when filled. A bonded material structure and thus sufficient dynamic loadability cannot be reached with this solution.
In DE 27 45 527, the production of outer rings of rolling bearings by using cold rolling is described. Two rings with exactly the same volume made of different materials are fixedly connected to one another by skrinking, then roll formed, and afterwards finish—machined by turning and grinding. The advantages are above all seen in the combination of the material characteristics, here above all in the combination of a ball race of great hardness with excellent wear characteristics and a support ring of reduced hardness and strength that can then be processed more easily. During forming, the rings are deformed together tangentially, radially and axially at the same time. A fast connection of both rings is reached only in exceptional cases. Different materials generally have different expansion capacities so that the rings tend to separate (the shrink connection separates) rather than to remain fixed together. For the technical implementation of the method, a complex tool configuration made of several divided tool parts is necessary. The costs are high; the production spectrum is limited and greatly curtailed in regard to complicated profile cross sections. In spite of the obvious advantages resulting from the potentially higher practical value of the composite rolling bearings, no large scale application of DE 27 45 527 is known.
The object of the invention is to efficiently produce annular composite workpieces, especially for high dynamic loads, made of at least two hollow cylindrical workpieces.